Stock-Based Employee Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012 Y	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to stock-based compensation plan	$ 84	$ 82	$ 81
Total income tax benefit related to stock-based compensation plan	29	29	28
Unrecognized compensation cost related to nonvested awards	77
Weighted average period of years over which unrecognized compensation cost will be reflected in operating results	1 year 8 months 12 days
Maximum number of shares in respect to which stock-based awards may be granted under the plan most recently approved by shareholders	8,650,000
Shares available for grant	7,317,721
Performance period in which performance unit awards are based	3 years
Stock option expiration period	10
Weighted average fair value per stock option granted	$ 11.95	$ 11.55	$ 9.46
Total intrinsic value of stock options exercised	40	35	37
Cash received from the exercise of stock options	47	53	58
Tax benefit realized with respect to the exercise of stock options	13	11	11
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share of the restricted stock units and performance units granted	$ 68.64	$ 60.58	$ 51.04
Total fair value of the restricted stock units and performance units vested	74	59	46
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share of the restricted stock units and performance units granted	$ 63.38	$ 64.34	$ 60.06
Total fair value of the restricted stock units and performance units vested	$ 70	$ 47	$ 53

Performance period in which performance unit awards are based.

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- Definition

The expiration period of stock options.

+ References

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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-Publisher FASB

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-Paragraph A240

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 64

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Name Accounting Standards Codification

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- Definition

Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

+ References

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- Definition

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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- Definition

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The total fair value of equity-based awards for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Name Accounting Standards Codification

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